JP4362961B2 - Orthogonal frequency division multiplexing modulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM modulation apparatus applied to digital broadcasting, a broadcast relay apparatus, and the like using an orthogonal frequency division multiplexing (OFDM) modulation system.
[0002]
[Prior art]
In recent years, a modulation scheme called orthogonal frequency division multiplexing (OFDM) has been proposed as a scheme for transmitting digital signals. In this OFDM modulation system, a number of orthogonal subcarriers (subcarriers) are provided in a transmission band, data is allocated to the amplitude and phase of each subcarrier, and PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation) is used. This is a digital modulation method. Since this OFDM modulation scheme divides the transmission band by a large number of subcarriers, the band per subcarrier is narrowed and the modulation speed is slow, but the total transmission speed is the same as the conventional modulation scheme. have. In addition, this OFDM modulation scheme has a feature that the symbol rate becomes slow because a large number of subcarriers are transmitted in parallel. Therefore, this OFDM modulation scheme can shorten the time length of the multipath relative to the time length of the symbol, and is less susceptible to multipath interference. In addition, since the OFDM modulation method assigns data to a plurality of subcarriers, an IFFT (Inverse Fast Fourier Transform) arithmetic circuit that performs inverse Fourier transform during modulation, and an FFT (Fast Fourier Transform) that performs Fourier transform during demodulation. ) It has a feature that a transmission / reception circuit can be configured by using an arithmetic circuit.
[0003]
From the above characteristics, the OFDM modulation scheme is widely studied to be applied to terrestrial digital broadcasting and communication that are strongly affected by multipath interference.
[0004]
Standards such as DVB-T (Digital Video Broadcasting-Terrestrial) and ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) have been proposed as terrestrial digital broadcasting employing such an OFDM modulation method.
[0005]
A transmission signal based on the OFDM modulation scheme is transmitted in symbol units called OFDM symbols as shown in FIG. This OFDM symbol is composed of an effective symbol that is a signal period during which IFFT is performed at the time of transmission, and a guard interval in which the waveform of the latter half of the effective symbol is copied as it is. This guard interval is provided in the first half of the OFDM symbol. For example, in the DVB-T standard (2K mode), 2048 subcarriers are included in an effective symbol, and the subcarrier interval is 4.14 kHz. Data is modulated to 1705 subcarriers out of 2048 subcarriers in the effective symbol. The guard interval is a signal having a time length of 1/4 of the effective symbol.
[0006]
First, a conventional OFDM modulation apparatus will be described. Here, an OFDM modulation apparatus according to the DBV-T standard (2K mode), which is one of the terrestrial digital broadcasting standards, will be described.
[0007]
As shown in FIG. 5, the conventional OFDM modulation apparatus 101 includes a MUX adaptation / energy spreading circuit 102, a Reed-Solomon encoder 103, a convolutional interleaving circuit 104, a convolutional encoder 105, and a bit / symbol interleaving. A circuit 106, a mapping circuit 107, a frame adaptation circuit 108, an IFFT circuit 109, a guard interval addition circuit 110, a D / A converter 111, an aperture correction circuit 112, a front end 113, an antenna 114, And a TPS generation circuit 114.
[0008]
An MPEG2 transport stream (Transport Stream) obtained by compressing and multiplexing video and audio signals by the preceding MPEG encoder is input to the OFDM modulation apparatus 101. This transport stream is supplied to the MUX adaptation / energy spread circuit 102 of the OFDM modulator 101.
[0009]
The MUX adaptation / energy diffusion circuit 102 reverses the bit of the synchronization byte 47h of the first byte of the TS packet for every eight TS packets to obtain B8h. At this time, a shift register for generating a pseudo-random number sequence (PRBS) used at the same time for energy diffusion is initialized with a predetermined seed every eight TS packets. In the DVB-T system, the PRBS sequence is (x ¹⁵ + X ¹⁴ +1) and the seed is 009Ah. The MUX adaptation / energy spreading circuit 102 performs an energy spreading process by performing an exclusive OR operation on the data excluding the synchronization byte (1 byte) of the TS packet and the PRBS. The data sequence subjected to energy spreading is supplied to the Reed-Solomon encoder 103.
[0010]
The Reed-Solomon encoder 103 performs Reed-Solomon encoding processing on the input data series, and adds 16-byte parity for each TS packet. The data sequence to which the parity is added is supplied to the convolutional interleave circuit 104.
[0011]
The convolutional interleaving circuit 104 performs convolutional interleaving processing in units of bytes on the input data series. For example, as shown in FIG. 6, the convolutional interleaving circuit 104 has 12 branches provided with delay elements having different delay amounts, selects the same branch for both input and output, and simultaneously selects 0 for each byte. , 1, 2, 3, 4,..., 10, 11, 0, 1, 2,. Then, 1-byte output is performed for 1-byte input, and convolutional interleaving is performed. The data sequence subjected to the convolutional interleaving is supplied to the convolutional encoder 105.
[0012]
The convolutional encoder 105 performs, for example, convolutional encoding with two encoders of G1 = 171 (Octal) and G2 = 133 (Octal), and performs 2-bit encoded output for 1-bit input. . Further, when puncturing is performed, puncturing is performed on the 2-bit encoded output. The data sequence subjected to the convolutional encoding is supplied to the bit / symbol interleave circuit 106.
[0013]
The bit / symbol interleaving circuit 106 performs interleaving of frequencies in the OFDM symbol and interleaving in bits assigned to mapping points. The interleaved data series is supplied to the mapping circuit 107.
[0014]
The mapping circuit 107 divides the data series with a code length corresponding to the modulation scheme (for example, a 6-bit code length in the case of 64QAM), and assigns each to a predetermined mapping point. By assigning the data series to the mapping points in this way, two-dimensional information consisting of I and Q components is output. The data series made into the two-dimensional information is supplied to the frame adaptation circuit 108.
[0015]
The frame adaptation circuit 108 inserts a predetermined pilot signal, a transmission path multiplexing control signal (TSP: Transmission Parameter Signaling) and a null signal supplied from the TPS generation circuit 114, in addition to the mapped two-dimensional information, so-called OFDM Perform frame configuration processing. The data series having the OFDM frame configuration is supplied to the IFFT circuit 109.
[0016]
The IFFT circuit 109 uses 2048 sets of data of I and Q as one OFDM symbol, and collectively performs IFFT calculation. The data series subjected to the IFFT calculation is supplied to the guard interval addition circuit 110 for each effective symbol.
[0017]
The guard interval adding circuit 110 copies the signal waveform of the second half of the signal of the effective symbol output from the IFFT circuit 109 and adds it to the head of the effective symbol, and adds a guard interval to the effective symbol. The data with the guard interval added is supplied to the D / A converter 111.
[0018]
The D / A converter 111 converts the digital signal into an analog signal and supplies it to the aperture correction circuit 112.
[0019]
The aperture correction circuit 112 corrects signal deterioration caused by the aperture effect of the D / A converter 111. Specifically, the aperture correction circuit 112 corrects the frequency characteristic according to the frequency characteristic of the aperture effect. The signal subjected to the aperture correction is supplied to the front end 113.
[0020]
The front end 113 performs frequency up-conversion of the aperture-corrected signal to the RF band and radiates it into the air via the antenna 114.
[0021]
[Problems to be solved by the invention]
By the way, in the conventional OFDM modulation apparatus 101, the aperture effect of the D / A converter is performed in the analog domain. For this reason, the circuit scale of the aperture correction circuit is increased, and it is difficult to correct the frequency characteristics to an optimum value.
[0022]
The present invention has been made in view of such a situation. For example, the frequency characteristic of the aperture effect by the D / A converter, the frequency characteristic of the transmission path, the frequency characteristic of the aperture effect by the A / D converter on the demodulation side, etc. An object of the present invention is to provide an orthogonal frequency division multiplex modulation device capable of correcting various frequency characteristics generated for a time-domain modulated signal with a simple configuration.
[0023]
[Means for Solving the Problems]
An orthogonal frequency division multiplex modulation apparatus according to the present invention is an orthogonal frequency division multiplex modulation apparatus that divides information into each frequency component (subcarrier) within a predetermined band and modulates the information, and has a predetermined number of subcarriers within the predetermined number of subcarriers. Configuration means for configuring a digital data sequence for each transmission symbol composed of the number of data, The value of each data of the digital data series configured by the above configuration means, For each transmission symbol Complement Correction means to correct, and Corrected by correction means Inverse Fourier transform means for allocating each data constituting a transmission symbol to a power level of each subcarrier in a predetermined band, performing inverse Fourier transform for each transmission symbol, and converting it to time domain data A digital / analog conversion means for converting the time domain data into an analog signal; The correction means includes: Of the inverse characteristics of the frequency characteristics of the aperture effect of the digital / analog conversion means, an intercept data storage unit for storing intercept data indicating the gain of the lowest subcarrier, and each frequency region in which the inverse characteristics are divided into a predetermined number A slope data storage unit that stores slope data indicating the slope of the average gain for each frequency domain, and a transmission symbol before being converted to the time domain data using the intercept data and the slope data Corresponding to each subcarrier in Data value For each frequency region, the correction that gives the reverse characteristics is performed. .
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an OFDM modulation apparatus to which the present invention is applied will be described as an embodiment of the present invention. Here, as an example, an OFDM modulation apparatus according to the DBV-T standard (2K mode), which is one of the terrestrial digital broadcasting standards, will be described.
[0028]
As shown in FIG. 1, the OFDM modulation apparatus 1 includes a MUX adaptation / energy spread circuit 11, a Reed-Solomon encoder 12, a convolutional interleaving circuit 13, a convolutional encoding circuit 14, and a bit / symbol interleaving circuit 15. A mapping circuit 16, a frame adaptation circuit 17, an aperture correction circuit 18, an IFFT circuit 19, a guard interval addition circuit 20, a D / A converter 21, a front end 22, a transmission antenna 23, and a TPS. And a generation circuit 24.
[0029]
The OFDM modulation apparatus 1 receives an MPEG2 transport stream in which video and audio signals are compressed and multiplexed by the previous MPEG encoder. This transport stream is supplied to the MUX adaptation / energy spread circuit 11 of the OFDM modulator 1.
[0030]
The MUX adaptation / energy diffusion circuit 11 bit-inverts the first one byte of the synchronization byte 47h of the TS packet for every eight TS packets to obtain B8h. At this time, a shift register for generating a pseudo-random number sequence (PRBS) used at the same time for energy diffusion is initialized with a predetermined seed every eight TS packets. The MUX adaptation / energy diffusion circuit 11 performs an energy diffusion process by performing an exclusive OR operation on the data excluding the synchronization byte (1 byte) of the TS packet and the PRBS.
[0031]
The MUX adaptation / energy diffusion circuit 11 has a 15th order (X ₁₅ + X ₁₄ Energy diffusion is performed using a pseudo-random sequence of +1). The data subjected to the energy spreading process is supplied to the Reed-Solomon encoder 12.
[0032]
The Reed-Solomon encoder 12 performs a Reed-Solomon encoding process on the input data series, and adds 16-byte parity for each TS packet. The data series to which the parity is added is supplied to the convolutional interleave circuit 13.
[0033]
The convolutional interleaving circuit 13 performs convolutional interleaving processing on the input data series. For example, as shown in FIG. 6, the convolutional interleaving circuit 13 has 12 branches provided with delay elements having different delay amounts. The same branch is selected for both input and output, and each byte is simultaneously selected. The branches are sequentially switched such as 0, 1, 2, 3, 4,... 10, 11, 0, 1, 2,. Then, 1-byte output is performed for 1-byte input, and convolutional interleaving is performed. The data sequence subjected to the convolutional interleaving is supplied to the convolutional coding circuit 14.
[0034]
The convolutional encoding circuit 14 performs convolutional encoding with two encoders, for example, G1 = 171 (Octal) and G2 = 133 (Octal), and performs 2-bit encoded output for 1-bit input. . Further, when puncturing is performed, puncturing is performed on the 2-bit encoded output. The data sequence subjected to the convolutional coding is supplied to the bit / symbol interleave circuit 15.
[0035]
The bit / symbol interleave circuit 15 performs frequency interleaving within the OFDM symbol and interleaving within the bits assigned to the mapping points. The interleaved data series is supplied to the mapping circuit 16.
[0036]
The mapping circuit 16 divides the data series with a code length corresponding to the modulation scheme (for example, a 6-bit code length in the case of 64QAM), and assigns each to a predetermined mapping point. By assigning the data series to the mapping points in this way, two-dimensional information consisting of I and Q components is output. The data series converted to two-dimensional information is supplied to the frame adaptation circuit 17.
[0037]
The frame adaptation circuit 17 inserts a predetermined pilot signal, a transmission path multiplexing control signal (TSP: Transmission Parameter Signaling) and a null signal supplied from the TPS generation circuit 24 in addition to the mapped two-dimensional information, into an OFDM frame Make the configuration.
[0038]
Here, when adopting the OFDM modulation scheme, generally, a data structure called an OFDM symbol is formed in a predetermined number of modulation symbol units (a set of I and Q data). An OFDM symbol is a data unit for performing IFFT operations in a lump, and each I and Q data in the OFDM symbol is assigned to each subcarrier. For example, in the DVB-T standard, the number of modulation symbols (I, Q data) transmitted in one OFDM symbol is 2048 (carrier numbers # 0 to # 2047), of which data effective for 1705 subcarriers. Is assigned.
[0039]
The OFDM frame creation unit 32 divides the input transmission data into such OFDM symbols and OFDM frame units to form a frame. The transmission data having the frame configuration is supplied to the aperture correction circuit 18.
[0040]
The aperture correction circuit 18 takes into account the frequency characteristics generated by the aperture effect of the D / A converter 21 at the subsequent stage, and corrects the reverse characteristics of the frequency characteristics generated by the aperture effect in advance to the transmission data in this frequency domain. Circuit. The transmission data subjected to the aperture correction is supplied to the IFFT arithmetic circuit 19.
[0041]
The IFFT circuit 19 uses 2048 sets of data of I and Q as one OFDM symbol and collectively performs IFFT calculation. The data series subjected to the IFFT calculation is supplied to the guard interval addition circuit 20 for each effective symbol.
[0042]
The guard interval adding circuit 20 copies the signal waveform of the latter half of the signal of the effective symbol output from the IFFT circuit 19 and adds it to the head of the effective symbol, and adds a guard interval to the effective symbol. The data with the guard interval added is supplied to the D / A converter 21.
[0043]
The D / A converter 21 converts a digital signal into an analog signal. The signal converted into the analog signal is supplied to the front end 22. The signal output from the D / A converter 21 is free from the influence of the aperture effect.
[0044]
The front end 22 performs frequency up-conversion of the signal supplied from the D / A converter 21 to the RF band and radiates it into the air via the transmission antenna 23.
[0045]
Next, the aperture correction circuit 18 will be described in more detail.
[0046]
As described above, the aperture correction circuit 18 considers the frequency characteristic caused by the aperture effect of the D / A converter 21 at the subsequent stage, and previously converts the inverse characteristic of the frequency characteristic caused by the aperture effect to the transmission data in this frequency domain. It is a circuit to give to.
[0047]
In OFDM modulation, transmission data is collectively processed in units of OFDM symbols to generate a time-domain signal in which each data value in the OFDM symbol is assigned as the power value of each subcarrier, and information frequency multiplexing is performed. I do. Therefore, if a predetermined gain is determined for each assigned frequency and the data value is amplified or attenuated, the frequency characteristics of the time domain signal after frequency multiplexing can be freely corrected. In the present invention, utilizing this, an aperture correction circuit 18 is provided in front of the IFFT circuit 19, and the frequency characteristics caused by the aperture effect of the D / A converter 21 are corrected in advance in this time domain state.
[0048]
First, frequency characteristics corrected by the aperture correction circuit 18 are shown in FIG.
[0049]
The correction value shown in FIG. 2 indicates the inverse characteristic of the frequency characteristic (frequency vs. gain) of the aperture effect of the D / A converter 21. The characteristic diagram of this correction value is created by examining the characteristics of the D / A converter 21 in advance.
[0050]
First, from the inverse characteristic of the aperture effect, the lowest frequency gain, that is, the gain to be given to subcarrier number 0 is calculated. This calculated value is defined as intercept data. Further, the inverse characteristic of the aperture effect is divided into a predetermined number of frequency regions. Here, subcarrier numbers 0 to 2047 are divided into eight regions. This division method may or may not divide the frequency equally. Subsequently, from this inverse characteristic, an average gain gradient (that is, an average of gain increase when one subcarrier is increased) is calculated for each frequency region. This is the inclination data for each area.
[0051]
The aperture correction circuit 18 performs aperture correction by a digital circuit as shown in FIG. 3 based on the intercept data and the inclination data for each region.
[0052]
FIG. 3 shows a circuit configuration diagram of the aperture correction circuit 18.
[0053]
The aperture correction circuit 18 includes a correction value data generation unit 31, first to third registers 32 to 33 for timing adjustment, a multiplier 34, and a clip circuit 35.
[0054]
The aperture correction circuit 18 includes transmission data (I and Q data) output from the frame adaptation circuit 17, a timing clock synchronized with the transmission data (I and Q data), and an OFDM symbol start indicating the start timing of the OFDM symbol. A flag is entered. The value of the OFDM symbol start flag becomes valid (1) at the timing synchronized with the first data of the OFDM symbol (that is, data of subcarrier number 0). Further, intercept data and inclination data of each region are input as initial setting signals of the aperture correction circuit 18.
[0055]
The aperture correction circuit 18 includes a register 40, a carrier counter 41, an inclination data table 42, an intercept data register 43, a first selector 44, a second selector 45, an adder 46, and a clip circuit 47. And a register 48.
[0056]
The carrier counter 41 is a counter circuit that counts timing clocks. The carrier counter 41 outputs a value from 0 to 2047 as its output value. The carrier counter 41 receives an OFDM symbol start pulse whose timing is adjusted by the register 40. The carrier counter 41 resets the count value to 0 when the OFDM symbol start pulse becomes valid (1). That is, the carrier counter 41 is a circuit that generates the subcarrier number of each I and Q data in synchronization with the I and Q data input to the aperture correction circuit 18.
[0057]
The subcarrier number generated from the carrier counter 41 is input to the inclination data table 42.
[0058]
The tilt data table 42 is a table that stores the previously calculated tilt data. The inclination data table 42 stores the inclination data for each area by addressing the area number. Each inclination data stored in the inclination data table 42 can be rewritten from the outside, and can be updated as necessary.
[0059]
A subcarrier number generated from the carrier counter 41 is input to the inclination data table 42. The inclination data table 42 converts the input subcarrier number into an area number, and outputs inclination data with the converted area number as an address.
[0060]
The intercept data register 43 is a register for storing the intercept data calculated previously. The intercept data stored in the intercept data register 43 can be rewritten from the outside, and can be updated as necessary.
[0061]
The first selector 44 is a circuit that selects and outputs either the inclination data output from the inclination data table 42 or the zero value. The first selector 44 selects one of the slope data and the zero value in accordance with the OFDM symbol start pulse whose timing is adjusted by the register 40. If the OFDM symbol start pulse is valid (1), a 0 value is selected and output, and if it is invalid (0), slope data is selected and output. That is, the first selector 44 outputs a 0 value at the synchronization timing of the first I and Q data (symbol number 0) of the OFDM symbol, and outputs gradient data at other timings.
[0062]
The second selector 45 is a circuit that selects and switches between intercept data output from the intercept data register 43 and correction value data multiplied by I and Q data described later. The second selector 45 selects one of intercept data and correction value data in accordance with the OFDM symbol start pulse whose timing is adjusted by the register 40. When the OFDM symbol start pulse is valid (1), intercept data is selected and output, and when it is invalid (0), correction value data is selected and output. That is, the second selector 45 outputs intercept data at the synchronization timing of the first I and Q data (symbol number 0) of the OFDM symbol, and outputs correction value data at other timings.
[0063]
The adder 46 adds the output data of the first selector 44 and the output data of the second selector 45. That is, the data output from the adder 46 outputs intercept data at the synchronization timing of the first I and Q data (symbol number 0) of the OFDM symbol, and at other timings, the slope of each symbol is added to this intercept data. A value obtained by accumulating data is output.
[0064]
The clip circuit 47 clips the data output from the adder 46 with a predetermined value in order to prevent aliasing at the time of overflow. The clipped data is stored in the register 48.
[0065]
The data stored in the register 48 becomes the correction value data for aperture correction using the I and Q data at the current timing.
[0066]
As described above, the correction value data generation unit 31 generates correction value data.
[0067]
The correction value data stored in the register 48 of the correction value data generation unit 31 is input to the multiplier 34.
[0068]
The multiplier 34 multiplies the correction value data by the I and Q data whose timing is adjusted by the first register 32 and the second register 33.
[0069]
By multiplying the I and Q data by the correction value data in this way, the inverse characteristic of the frequency characteristic caused by the aperture effect of the D / A converter 21 is given to the transmission data in this frequency domain.
[0070]
The I and Q data corrected by the multiplier 34 is supplied to the clip circuit 35.
[0071]
The clip circuit 35 clips the I and Q data output from the multiplier 34 with a predetermined value in order to prevent aliasing at the time of overflow.
[0072]
Then, the clipped I and Q data are stored in the third register 36 and supplied to the subsequent IFFT arithmetic circuit 19 as corrected I and Q data.
[0073]
As described above, in the OFDM modulation apparatus 1 according to the embodiment of the present invention, the value of each data in the OFDM symbol before the IFFT calculation is corrected according to the frequency characteristic generated by the aperture effect of the D / A converter 21. .
[0074]
For this reason, the OFDM modulation apparatus 1 can correct the value of each data in the frequency domain before the IFFT calculation. Therefore, the aperture effect of the D / A converter 21 is corrected with a simple configuration using a digital circuit. be able to. Further, since each data is corrected in the frequency domain, an approximation close to the original characteristic can be performed, and an optimal correction can be performed. Further, since the correction is performed by the digital circuit, the correction value can be easily changed from the outside, and the frequency characteristic can be easily changed.
[0075]
In correcting the aperture effect, the frequency area of the data to be IFFT-calculated is divided to obtain the slope value for each area. However, if the number of area divisions is increased, the required memory capacity increases. Aperture correction can be performed more accurately.
[0076]
In the aperture correction circuit 18, not only the frequency characteristic of the aperture effect but also the frequency characteristic of the transmission path and the frequency characteristic of the aperture effect generated by the A / D converter on the demodulation side can be corrected in advance. That is, it is possible to correct all the frequency characteristics generated for the time domain data after the IFFT calculation.
[0077]
【The invention's effect】
In the orthogonal frequency division multiplexing modulator according to the present invention, Using the intercept data and the slope data, correction for giving the inverse characteristic is performed for each frequency domain on the data value corresponding to each subcarrier in the transmission symbol before being converted to the time domain data. .
[0078]
For this reason, this orthogonal frequency division multiplexing modulator can correct the value of each data in the frequency domain before inverse Fourier transform. , D / A converter aperture effect Changes in frequency characteristics caused by time-domain modulated signals Can be corrected with a simple configuration using a digital circuit. Also, Using intercept data and slope data Each data For each divided frequency region Since correction is performed, approximation close to the original characteristic can be performed, and optimal correction can be performed. Further, since the correction is performed by the digital circuit, the frequency characteristic can be easily changed.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of the OFDM modulation unit.
FIG. 2 is a diagram illustrating an inverse characteristic of a frequency characteristic caused by an aperture effect of a D / A converter.
FIG. 3 is a circuit configuration diagram of the aperture correction circuit.
FIG. 4 is a diagram for explaining a signal structure of an OFDM symbol.
FIG. 5 is a block diagram of a conventional OFDM modulation apparatus.
FIG. 6 is a diagram for explaining a configuration of a convolutional interleaving circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wireless relay system, 11 Wireless camera, 12 Receiving relay station, 23 OFDM modulation part, 34 OFDM demodulation part, 42 MUX adaptation / energy spreading part, 87 MUX adaptation / energy de-spreading part

Claims (1)

In an orthogonal frequency division multiplex modulation apparatus that divides and modulates information into frequency components (subcarriers) within a predetermined band,
Configuration means for configuring a digital data sequence for each transmission symbol composed of a predetermined number of data within the number of subcarriers,
The value of each data of the digital data sequence which is constituted by the arrangement means, and compensation for correcting means for each of the transmission symbol,
Inverse Fourier transform that assigns each data constituting the transmission symbol corrected by the correction means to the power level of each subcarrier in a predetermined band, performs inverse Fourier transform for each transmission symbol, and converts it to time domain data Means ,
Digital / analog conversion means for converting the time domain data into an analog signal ;
The correction means is
An intercept data storage unit for storing intercept data indicating the gain of the lowest subcarrier among the inverse characteristics of the frequency characteristics of the aperture effect of the digital / analog conversion means;
An inclination data storage unit that stores, for each frequency domain, inclination data indicating an average gain inclination in each frequency domain in which the inverse characteristic is divided into a predetermined number;
Using the intercept data and the slope data , a correction that gives the inverse characteristic is performed for each frequency domain with respect to the data value corresponding to each subcarrier in the transmission symbol before being converted to the time domain data. An orthogonal frequency division multiplex modulation device to perform .

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